I really like the idea, and I especially like that you have a vegan-friendly version. Hope you are adding this to the adult series soon, as blogged in spring.
FYI: A friend of mine just bought some vegan boots @greenshoes.co.uk - if you have trouble with your material, you should check their stuff. It's Lorica, a microfibre-based material. The upper part looks and almost feels like leather, and it seems durable enough. Lower part is fabric, feels really nice on touch. It's even supposed to be breathable. Don't know how eco-friendly it is, though - it's manufactured by DuPont.